The aim of this study is to evaluate the incidence of tumors of the head and neck in a population treated for ringworm of the scalp (tinea capitis) with x-rays between 1940 and 1959, as compared with a similar group who received only topical medications for that condition during the same time period. The study consists of about 2200 irradiated subjects and 1400 unirradiated, control subjects, who will have an average follow-up interval of 35 yr. The primary tumor sites of interest are the skin, central nervous system (CNS) and the thyroid gland. Regarding skin cancer of the head and neck, the study will provide information about: (a) the magnitude and (b) the temporal distributiion of skin cancer induction by ionizing radiation; (c) possible synergism between ultraviolet radiation (UVR) and ionizing radiation in skin cancer induction; (d) the role of host-susceptibility complexion factors in radiogenic skin cancer; and (e) the rates of second-primary skin cancer occurrence among the cases. A determatologic clinical evaluation program for a subsample of subjects will supplement the cohort follow-up data. The incidence of thyroid cancers and adenomas will be ascertained to determine if there is an excess in the irradiated group. This is one of the few studies with a substantial number of subjects with low doses (about 6 rad) to the thyroid. The incidence of central nervous system (CNS) tumors will be documented and the magnitude of CNS tumor induction related to radiation dose (average brain dose of (about 140 rad). The study will also provide evidence on the temporal distribution of and possible host susceptibility factors for radiogenic CNS tumors.